Compiling language definitions: the ASF+SDF compiler

The ASF+SDF Meta-Environment is an interactive language development environment whose main application areas are definition of domain-specific languages, generation of program analysis and transformation tools, production of software renovation tools, and general specification and prototyping. It uses conditional rewrite rules to define the dynamic semantics and other tool-oriented aspects of languages, so the effectiveness of the generated tools is critically dependent on the quality of the rewrite rule implementation. The ASF+SDF rewrite rule compiler generates C code, thus taking advantage of C's portability and the sophisticated optimization capabilities of current C compilers as well as avoiding potential abstract machine interface bottlenecks. It can handle large(10 000+ rule) language definitions and uses an efficient run-time storage scheme capable of handling large (1 000 000+ node) terms. Term storage uses maximal subterm sharing (hash-consing), which turns out to be more effective in the case of ASF+SDF than in Lisp or SML. Extensive benchmarking has shown the time and space performance of the generated code to be as good as or better than that of the best current rewrite rule and functional language compilers

Studying the evolution of software through software clustering and concept analysis

This thesis describes an investigation into the use of software clustering and concept analysis techniques for studying the evolution of software. These techniques produce representations of software systems by clustering similar entities in the system together. The software engineering community has used these techniques for a number of different reasons but this is the first study to investigate their uses for evolution. The representations produced by software clustering and concept analysis techniques can be used to trace changes to a software system over a number of different versions of the system. This information can be used by system maintainers to identify worrying evolutionary trends or assess a proposed change by comparing it to the effects of an earlier, similar change. The work described here attempts to establish whether the use of software clustering and concept analysis techniques for studying the evolution of software is worth pursuing. Four techniques, chosen based on an extensive literature survey of the field, have been used to create representations of versions of a test software system. These representations have been examined to assess whether any observations about the evolution of the system can be drawn from them. The results are positive and it is thought that evolution of software systems could be studied by using these techniques

A virtual machine framework for domain-specific languages

Experts in a field regularly apply a defined set of rules or procedures to carry out a problem-solving task or analysis on a given problem. Often the problem can be represented as a computer model, be it mathematical, chemical, or physics based, and so on. It would certainly be advantageous for a domain expert who is not proficient in software development to express solutions to problems in a domain-specific notation that can be executed as a program. Many new ideas aim to make software development easier and shift the development role closer to the end-user. One such means of development is the use of a small, intuitive programming language called a Domain-Specific Language (DSL.) This dissertation examines a generic approach to constructing a Virtual Machine (VM) to provide the runtime semantics for a particular DSL. It proposes a generic, object-oriented framework, called a VM Framework, in which to build a VM by subtyping abstract instruction and environment classes that are part of the VM Framework. The subtyped classes constitute an environment and an interface called an instruction set architecture and the instructions can access and operate on the environment in a deterministic way to provide the runtime semantics of a DSL program. Both instruction classes and environment classes encapsulate functionality of an existing domain, represented programmatically as a namespace construct. The namespace is home to related classes that provide the various concepts inherent of a domain. These are concepts understood by a domain expert and in this dissertation it is shown how they are exposed as DSL constructs. With the use of compiler writing tools, a compiler can be created for a DSL that generates an appropriate instruction sequence that can be executed by the VM. The grammar of the DSL is shown to feature constructs that allow a domain expert to express concepts of the underlying domain in an intuitive manner. The dissertation details how a VM is configured for a specific set of instructions and an environment. Instruction sets and environments can be extended creating VMs with additional semantics for DSLs that are similar, or contain subsets of semantics of other DSLs. The languages are intended to be intuitive and it is shown using examples how a specific DSL program is mapped to an instruction sequence with the instruction set architecture and environment in mind. Comparative performance in relation to other DSL implementations, including a hard-coded approach of a VM and an interpreted approach are also provided. The VM Framework is proven to be most effective in rapidly prototyping a DSL for a particular problem domain. The dissertation also provides examples of DSLs such as a real-valued expression language and a scene description language that uses a ray-tracer for rendering geometric objects onto a canvas. It is shown how the scene description language is an extension to the real-valued expression language in terms of their underlying VMs. All DSL grammars are provided.Dissertation (MSc (Computer Science))--University of Pretoria, 2007.Computer ScienceMScunrestricte

Managing software evolution in embedded systems

Verhoef, C. [Promotor]Klusener, A.S. [Copromotor

Bit-to-board analysis for IT decision making

Verhoef, C. [Promotor]Peters, R.J. [Copromotor

Evolution of batch-oriented COBOL systems into object-oriented systems through unified modelling language.

Throughout the world, there are many legacy systems that fulfil critical business functions but often require new functionality to comply with new business rules or require redeployment to another platform. Legacy systems vary tremendously in size, functionality, type (such as batch-oriented or real-time), programming language source code, and many other factors. Furthermore, many of these legacy systems have missing or obsolete documentation which makes it difficult for developers to re-develop the system to meet any new functionality. Moreover, the high cost of whole scale redevelopment and high switchover costs preclude any replacement systems for these legacy systems. Reengineering is often proposed as a solution to this dilemma of high re-development and switchover costs. However, reengineering a legacy system often entails restructuring and re-documenting a system. Once these restructuring and re-documentation processes have been completed, the developers are better able to redevelop the parts of the systems that are required to meet any new functionality. This thesis introduces a number of methods to restructure a procedurally-structured, batch-oriented COBOL system into an object-oriented, event-driven system through the use of an intermediate mathematical language, the Wide Spectrum Language (WSL), using system source code as the only documentation artefact. This restructuring process is accomplished through the application of several algorithms of object identification, independent task evaluation, and event identification that are provided in the thesis. Once these transformations are complete, method(s) are specified to extract a series of UML diagrams from this code in order to provide documentation of this system. This thesis outlines which of the UML diagrams, as specified in the UML Specifications version 1.5, can be extracted using the specified methods and under what conditions this extraction, using system source code only, can occur in a batch-oriented system. These UML diagrams are first expressed through a WSL-UML notation; a notation which follows the semantics and structure of UML Specifications version 1.5 in order to ensure compatibility with UML but is written as an extension of WSL in order to enable WSL to represent abstract modelling concepts and diagrams. This WSL-UML notation is then imported into a visual UML diagramming tool for the generation of UML diagrams to represent this system. The variety of legacy systems precludes any universal approach to reengineering. Even if a legacy system shares a common programming language, such as COBOL, the large number of COBOL constructs and the huge number of possible dialects prevents any universal translator of the original program code to another. It is hoped that by focusing on one particular type of legacy system with constraints, in this case a batch-oriented COBOL system with its source code its only surviving artefact, and by providing validated algorithms to restructure and re-document these legacy systems in the Unified Modelling Language, an industry system modelling standard, and by determining which of these Unified Modelling Language can be extracted practically from such a system, some of the parameters and uncertainties, such as program understanding of an undocumented system, in reengineering this type of system can be reduced

Мотив падения мятежных ангелов в западноевропейской живописи XV-XVII веков

Статья об особенностях иконографии сюжета падения мятежных ангелов в живописи стран Западной Европы эпохи Возрождения и маньеризм